Aerosol precipitor

ABSTRACT

An apparatus for precipitating aerosol particles comprises at least one pair of tubular elements placed one inside the other and forming an annular working space. The inner tubular element is connected to a source of steam or liquid to be evaporated and is made porous to enable penetration therethrough of the steam or liquid to be evaporated into the working space. The outer tubular element is maintained at a temperature below that of the inner tubular element and rotary motion is imparted to the aerosol flow in the annular working space by means of rotary blades.

United States Patent [191 Koka [54] AEROSOL PRECIPITOR [76] Inventor:Volodlmir Petrovlch Koka, ul. Kikvidze 3, Kv. l0, Kiev, U.S.S.R.

Filed: July 19, 1971 Appl. No.: 164,032

Related US. Application Data Continuation of Ser. No. 764,803, Oct. 3,1968, abandoned.

[52] US. Cl. ..55/222, 55/225, 55/226, 55/229, 55/230, 55/233, 55/235,55/240, 55/260, 55/269, 55/348, 55/457, 159/5, 202/187, 261/62, 261/79A, 261/94, 261/101 Int. Cl. ..B0ld 47/00 Field of Search ..55/267269,235-238, 55/209, 456 457, 222, 225, 226,

[ 51 May 22, 1973 [56] References Cited UNITED STATES PATENTS 5/1938Hickman ..202/l87 X 12/1939 Cornell, Jr... ..26l/l0l X 10/1966 Parson..202/l87 X Primary Examiner-Dennis E. Talbert, Jr. Attorney-Waters,Roditi & Schwartz [57] ABSTRACT 1 1 Claims, 4 Drawing Figures AEROSOLPRECIPITOR This application is a continuation of applicants copendingapplication Ser. No. 764,803, filed Oct. 3, 1968, now abandoned.

The invention relates to devices for precipitating aerosol particles,i.e. high-dispersing solid and/or liquid particles suspended in gas, andmay be utilized in many industrial branches, specifically, for dustcatching, gas cleaning, air sterilization, etc. 7

Commonly known is a dust precipitator, wherein a flow of dusty airpasses between wet surfaces of differing temperatures. The precipitatoris made as a chamber divided in height into three compartments by meansof horizontal heat-conducting partitions. The lower compartment servesto house the heating means, while the upper one accommodates the coolingmeans. The middle compartment thus has a lower, heated, wall and anupper, cooled, wall. Fed to the middle compartment through pipeconnections is water which fills par; tially the middle compartment andis evaporated under the effect of heat radiated by the lower heatedwall. Also fed to the same middle compartment is dusty air subject tocleaning, which, mixing with water vapor and coming into contact withthe upper cooled wall, is supersaturated with vapors, which leads to anincreased condensation of dust particles present in the air. The thusformed drops of the condensation fog are precipitated in a coil providedin the upper compartment of the installation under the action of theforces of inertia developing when the flow turns in the coil ducts.

The known precipitator is bulky and does not permit intensification ofthe condensation growth of lowactive particles. This latter disadvantageis due to the fact that because of the lack of uniformity in the vaporcondensation of particles suspended in gas, which, as a rule, are ofvarying sizes (varied dispersion composition) and of differing physicaland chemical activity (different moisture-imbibing capacity, solubilityetc.), the condensation involves larger and physically and chemicallymore active particles imbibing most of the excess moisture, which factresults in a reduced supersaturation of the flow on these portions andthe absence of condensation on smaller and little-active particles. As aresult, the growth of the latter is slowed down or discontinuedaltogether, and they freely fall through precipitation devices providedbehind the supersaturation chamber, without being caught in saiddevices.

It is an object of the present invention to provide an aerosolprecipitator permitting increase of the condensation growth oflow-active particles, and rather inexpensive and simple in construction,easy to mount and service, as well as allowing automatic control of theintensity of the supersaturation of the flow depending upon the valuesof the forces of interia, developed by the moving flow.

According to the above-mentioned and other objects, the aerosolprecipitator, in which the aerosol flow proceeds in a working spacelimited by walls having different temperature at a simultaneous feed ofvapor to said working space from the side of a wall heated to a highertemperature so as to insure supersaturation of the flow with vapor andthe condensation growth of aerosol particles to facilitate theirseparation from the flow under the action of the forces of inertia,according to the invention, comprises at least one pair of tubularelements inserted one into the other and forming an an- I Rotary motionmay be imparted to the aerosol flow with the aid of a screw-typeeddy-producing device installed preferably in the annular working spaceof the precipitator.

The tubular elements inserted one into the other may be made tapered andarranged with the possibility of axial displacement of one about theother.

The inner tapered tubular element is preferably made m such as to expandwith its wider section toward the top of the precipitator, said elementbeing immovably connected with the top eddy-producing device at theplace of this wider section, said eddy-producing device freely restingagainst the top end of the outer tubular element to insure unimpededaxial displacement of the inner tapered tubular element under the actionof the ascending aerosol flow.

The invention will be more apparent from the description of an exemplaryembodiment thereof and appended drawings, wherein:

FIG. I shows an aerosol precipitator, according to the invention, in alongitudinal section with tubular elements made cylindrical;

FIG. 2 is a section taken on line lI-Il as'in FIG. 1;

FIG. 3 is the same precipitator with several pairs of parallel tubularelements which are made tapered and expanding with their wider sectiontoward the precipitator bottom; and

FIG. 4 is the same precipitator with tubular elements made tapered andexpanding with their wider section toward the precipitator top.

FIGS. 1 and 2 show an exemplary embodiment of the apparatus wherein theworking area is formed bytwo coaxial cylindrical tubes, i.e. the outertube'l and the inner tube 2. In the annular space between said tubesthere are arranged screw-type eddy-producing devices 3 imparting rotarymotion to the aerosol flow, either of them being a cut portion of amultithread worm.

These also serve as a means for centering the tube 2 along the axis ofthe tube 1.

The outer tube 1 is provided with a jacket 4 in which a cooling liquidfed through branch pipes S is circulating, while the inner tube 2 ismade porous to receive vapor or a liquid liable to vaporization, throughbranch pipes 6, and heated either prior to its feed to the porous tube 2or right inside this tube.

Heating of the liquid right inside the tube 2 is effected, by passingthrough said tube electric current supplied to the inlet and outletbranch pipes 6. In this case, the tube 2 and the pipes 6 should beisolated from the outer tube 1, for which purpose the eddy-producingdevices 3 are manufactured from plastic or other electric-insulatingmaterial, while the branch pipes 6 are separated from the tube 1 byelectric-insulating bushes.

Thus, in the course of the precipitator operation, differenttemperatures are maintained in the tubes 1 and 2, the temperature of theouter tube 1 being lower than that of the tube 2. In the annular workingspace limited by differently heated walls of the tubes 1 and 2, with asimultaneous feed into the working space of vapor from the side of thehigher temperature tube 2, supersaturation uniform throughout the entireheight of the precipitator is insured, providing the condensation growthof particles of the aerosol flow proceeding in the annular space. Themore the temperature difference, the higher the supersaturation of theflow.

Yet, the temperature difference is preferably increased not by raisingthe vapor temperature but by decreasing the temperature of the cooledtube 1. In addition to making use of the cooling jacket, the cooling ofthe tube 2 may be achieved, e.g., with the aid of coils when coolantsfrom cooling installations are utilized, as well as by means of anyother cooling means.

The means for imparting rotary motion to the aerosol flow may also befashioned as inlet and outlet branch pipes tangentially attached to thetube 1 and serving to introduce aerosol and discharge purified gas, asis the case in common cyclones (not shown in Figs), or may have someother embodiment, preferably such as would permit transformation of theaxial gas flow into a rotary flow, with minimum losses of kinetic energyof the moving aerosol.

In the proposed precipitator, the tube 1 may be made both stationary orrotary. The eddy-producing devices 3 may also be stationary or rotary.

The proposed apparatus may be made as separate interchangeable sectionsshown in FIG. 1, which can be then attached one to another successivelyon the flanges with sealing gaskets. The height of each section, as wellas their required number, is established through calculations orexperimentally depending upon the amount of the aerosol passing throughthe precipitator, initial moisture and temperature of the aerosol,dispersion ability and fractional composition of suspended particles andtheir moisture-imbibing capacity, required degree of precipitation ofaerosol particles, etc.

In case the vapor tube 2 and the cooled tube 1 are made of similarlength, the gas freed from aerosol particles or air at the outlet fromthe precipitator top mouth will have approximately 100 percent moisturecontent.

If it is necessary to have the exhaust gas or air of a predeterminedmoisture and temperature, the porous tube 2 should be made shorter thanthe outer tube 1. In this case, the upper portion of the cooled tube 1will be used as a gas cooler. The gas being cooled, its moisture is alsodecreased.

An additional cooling surface for the exhaust gas may be obtained byattaching one more section having no inner vapor tube 2 to the topportion of the precipitator.

To insure treatment in the precipitator of large volumes of aerosol, theapparatus may comprise several parallel pairs of the tubes 1 and 2, theouter tubes 1 possibly having both cooling means individual for each ofthe tubes 1 a cooling device common to all of the parallel tubes. Saidcooling device may be fashioned as a common cooling jacket (as shown inFIG. 3) fitted with branch pipes for the supply of the cooling liquid.

If it is necessary to regulate the intensity of supersaturation createdin the annular working space of the precipitator without varying theestablished difference in the temperatures of the walls of the tubularelements, both the outer and inner tubular elements should be madetapered.

FIG. 3 shows such tapered tubular elements 1 and 2 expanding with theirwider sections toward the bottom of the precipitator. Hereafter, thetapered tubular elements are referred to as tapered tubes.

The outer tapered tubes 1 of the precipitator shown in FIG. 3 have acommon cooling device made as a reservoir jacket 4 fitted with branchpipes 5 to feed and discharge the cooling liquid. J

The eddy-producing devices 3 of the aerosol flow are provided at theinlet of the aerosol flow and at its outlet from the annular workingspace in cylindrical pipe sockets 7 attached to the ends of the outertapered tube 1. The branch pipes 6 for feeding and removing the vapor ora liquid liable to evaporation are made as flexible hoses in theprecipitator bottom and as cut portions of metal pipes in the top of theapparatus, said out portions being attached to a metal tube, 8 closed inits ends and connected, in its turn, with a flexible hose.

The metal tube 8 is at the same time a crosspiece intended for liftingand lowering the tapered tubes 2. Attached to both ends of the tube 8are ropes 9 wound on drums 10 and unwound from them when varying thedirection of rotation of axle 11. By displacing the inner vapor tubes 2about the cooled tubes 1, it is possible to vary the annular gap betweenthe tubes and, consequently, the intensity of supersaturation in theworking space of the precipitator.

A relative displacement of the tapered tubes 1 and 2 may be effected inother ways, too, e.g. with the aid 'of an electromagnet (not shown inthe drawing) whose core can be linked with the inner tubes 2. By varyingthe strength of the electric current supplied to the electromagnet coil,the inner tubes 2 may be lifted and lowered.

To make possible automatic control of the intensity of the flowsupersaturation depending upon the value of centrifugal forces developedby the moving flow, the tapered tubes 1 and 2 (FIG. 4) should beinstalled with their wider section above. Besides, each inner taperedtube 2 with the eddy-producing devices 3 attached to it should be sopositioned in the precipitator that, when being out of operation, itshould freely rest against the upper end of the outer tube 1 with theupper eddy-producing device 3 and, when in operation and with theaerosol flowing through the apparatus, it should freely soar in theascending flow of the latter. The higher the speed of the aerosol motionand, consequently, the centrifugal forces developed in the course of itseddying, the greater the gap between the tubes. This permits automaticcontrol of the intensity of the supersaturation created in theprecipitator, depending upon variations in the value of the centrifugalforces.

To prevent spontaneous rotation of the inner tube 2 (FIG. 4) as a resultof the pressure of the ascending gas flow on the blades of theeddy-producing devices 3, a plank l2 resting against a stop 13 may beattached to one of said eddy-producing devices.

The general operational principle of the proposed precipitatorisdescribed hereinbelow only for the first embodiment, since theoperational principle in the other cases is analogous.

Vapor or a hot liquid is brought to the porous tube 2, which isevaporated from the tube outer surface into the annular space between itand the outer cooled tube 1 in whose water jacket cold water or othercooling liquid is circulating. Thus, in the course of the precipitatoroperation, the tube 1 and the tube 2 are maintained at diffeferenttemperatures. The greater the temperature difference, the higher thesupersaturation of the flow.

The aerosol flow is fed to the apparatus mostly from the bottom upwards;eddying at the inlet and rotating in the annular gap between thedifferently heated surfaces of the tubes 1 and 2, the flow issupersaturated with vapor. Owing to the uniform distribution of thevapor throughout the height of the annular gap, made possibile by theuse of the porous tube 2, the supersaturation of the flow is alsouniform throughout all of its path in the annular working space of theprecipitator.

Aerosol particles suspended in the flow, in the course of theircondensation growth, are incessantly deposited on the precipitator wallsunder the action of centrifugal forces developing in the course of theflow rotation, owing to which conditions are created for involving lessactive particles into the process of condensation growth. As a result,all suspended particles are separated from gas directly in the annularspace between the tubes 1 and 2.

Drops of the emerging condensation fog, thrown back onto the inner wallof the cooled tube 1, merge into a fluid film which runs down the walls,carrying with it the trapped particles into the bottom portion of theprecipitator, predominantly into a hopper provided with a gate (notshown in the drawing).

In the course of the apparatus operation, the difference of thetemperatures on the walls of the tubes 1 and 2 should be maintained sothat the temperature of the tube 2 penetrable for vapor or a liquidliable to evaporation be enough to insure uniform supply of the vaporinto the working space of the precipitator, while the temperature of thecooler tube 1 should be sufficient to insure a required intensity ofsupersaturation of the aerosol flow being treated in said precipitator.

In practice, when using different liquids for vapor generation, thetemperature of the tube 2 penetrable for a particular liquid should bemaintained on the level of the boiling point of a selected liquid or 5to C lower than this point. In case vapor is used, the temperature ofthe tube 2 penetrable for a selected vapor should be kept higher thanits condensation point.

When using water vapor or the vapor of other liquids with a higherboiling point (higher than 100 C), the temperature of the both tubes 1and 2 may be above zero, e.g. the temperature of the tube may be 145 Cand of the tube 1, 20 C.

When using the vapors of low-boiling liquids, the temperature of thetube 2 may be above zero, e.g. 60 C, and the temperature of the tube 1subzero, e.g. 30 C. In the case of using liquefiable gases, thetemperature of both tubes may be subzero, e.g. when using propane whosecondensation point is 42.l C, the temperature of the tube 2 may be 20 C,while that of the tube 1 100 C.

Liquefiable gases and, correspondingly, the subzero temperatures of thetubes 1 and 2 are most suitable when effecting the process ofcondensation or freezing vapors from gas or air with a simultaneousseparation of emerging drops or crystalls. Liquefiable gases, condensingon the particles of a newly emerging phase, make these particles heavierand facilitate their separation from the flow under the action ofcentrifugal forces.

Used as vapor brought into the tube 2 penetrable for them may be variouschemically generated secondary vapor, e.g. volatile solvents removedfrom solutions by evaporation. The proposed apparatus permits the use ofthese solvents for condensation precipitation of the aerosol particleswith a simultaneous regeneration of these solvents for their furtherutilization. Utilized analogously may be waste vapors from variousplants as well as hot discharge (drain) liquids.

Furthermore, the precipitator may also be used for different combinedprocesses. Thus, in addition to the process of precipitation of aerosolparticles, the apparatus may also be employed for evaporative cooling ofhot liquid and (or) heating of cold liquid by regulating the temperatureof outgoing liquids through variations in the speed of their travelinside the porous tube 2 and (or) in the cooled jacket 4.

The proposed precipitator may also be used as a dis tillation apparatuswherein it is possible to effect the condensation trapping of bacteriaand other particles suspended in the air along with the evaporation ofvolatile solvents from a complex solution and the regeneration of thesesolvents.

The precipitator is particularly suitable for such combined processes ofheator mass-exchange which are most effective in conditions of phasetransformations and in temperature spheres close to evaporation(condensation) points of substances involved in the abovesaid processes.

I claim:

1. An aerosol precipitator connected to a source of fluid such as vaporor liquid subject to evaporation and comprising: at least one pair oftubular elements inserted one into the other and forming an annularworking space therebetween for passage of an aerosol flow therethrough,the inner element being made porous and penetrable to the fluid subjectto evaporation, means for supplying said fluid within the inner element;cooling jacket means surrounding the outer element and extendinglengthwise over the outer element over at least a major portion thereofwhich circumscribes said inner element for maintaining said outerelement at a temperature lower than that of said inner tubular elementto provide a difference of temperature between said tubular elementssufficient to effect supersaturation of the aerosol flow with vapor andsecure condensation growth of the aerosol particles; said means forsupplying fluid to the inner element comprising a tube connected to oneendof the inner element for supply of fluid thereto, and a tubeconnected to the other end of the inner element for removal of fluidtherefrom, and means disposed adjacent said one end to the inner elementfor imparting rotary movement to the aerosol flow in said annularworking space to provide for the deposition of condensation growingaerosol particles from the flow, under the action of centrifugal forcesproduced in the course of rotation of said flow.

2. A precipitator according to claim 1 wherein said means for impartingrotary movement to the aerosol flow in the annular working spacecomprises a screwtype eddy-producing device disposed in said annularworking space.

3. A precipitator according to claim 1 wherein said tubular elements aretapered and supported for relative axial displacement to adjust the sizeof the space between the tubular elements and thus regulate theintensity of supersaturation of the aerosol flow while maintaining thetemperature difference between the tubular elements.

4. A precipitator according to claim 1 wherein said tubular elements aresubstantially coextensive in length.

5. A precipitator according to claim 1 wherein said cooling jacket meansfor maintaining a lower temperature on the outer tubular elementcomprises a jacket for a cooling liquid surrounding the outer tubularelement.

6. A precipitator according to claim I wherein said tubular elements arevertical.

7. A precipitator according to claim 1 wherein said tubular elements arevertical and said means for imparting rotary movement comprises a screwtype device, both at the top and bottom of said space.

8. A precipitator according to claim 6 wherein said tubular elementswiden upwardly.

9. A precipitator according to claim wherein said cooling jacket'meansfor maintaining the outer element at a temperature lower than the innerelement includes means for circulating a cooling liquid therethrougharound said outer element.

10. A precipitat'or according to claim 3 wherein said tubes areflexible.

l l. A precipitator according to claim 10 wherein said tubular elementsare vertical and said one end of the inner element is the lower endthereof and the other end of the inner element is the upper end thereof,said precipitator further comprising a branch pipe for conveying fluid,said branch pipe being connected to the upper end of the inner elementand to said tube at the upper end to interconnect the same and means forraising and lowering the inner element within the outer elementincluding means coupled to said branch pipe to raise and lower the sameand the inner element therewith.

1. An aerosol precipitator connected to a source of fluid such as vaporor liquid subject to evaporation and comprising: at least one pair oftubular elements inserted one into the other and forming an annularworking space therebetween for passage of an aerosol flow therethrough,the inner element being made porous and penetrable to the fluid subjectto evaporation, means for supplying said fluid within the inner element;cooling jacket means surrounding the outer element and extendinglengthwise over the outer element over at least a major portion thereofwhich circumscribes said inner element for maintaining said outerelement at a temperature lower than that of said inner tubular elementto provide a difference of temperature between said tubular elementssufficient to effect supersaturation of the aerosol flow with vapor andsecure condensation growth of the aerosol particles; said means forsupplying fluid to the inner element comprising a tube connected to oneend of the inner element for supply of fluid thereto, and a tubeconnected to the other end of the inner element for removal of fluidtherefrom, and means disposed adjacent said one end to the inner elementfor imparting rotary movement to the aerosol flow in said annularworking space to provide for the deposition of condensation growingaerosol particles from the flow, under the action of centrifugal forcesproduced in the course of rotation of said flow.
 2. A precipitatoraccording to claim 1 wherein said means for imparting rotary movement tothe aerosol flow in the annular working space comprises a screw-typeeddy-producing device disposed in said annular working space.
 3. Aprecipitator according to claim 1 wherein said tubular elements aretapered and supported for relative axial displacement to adjust the sizeof the space between the tubular elements and thus regulate theintensity of supersaturation of the aerosol flow while maintaining thetemperature difference between the tubular elements.
 4. A precipitatoraccording to claim 1 wherein said tubular elements are substantiallycoextensive in length.
 5. A precipitator according to claim 1 whereinsaid cooling jacket means for maintaining a lower temperature on theouter tubular element comprises a jacket for a cooling liquidsurrounding the outer tubular element.
 6. A precipitator according toclaim 1 wherein said tubular elements are vertical.
 7. A precipitatoraccording to claim 1 wherein said tubular elements are vertical and saidmeans for imparting rotary movement comprises a screw type device, bothat the top and bottom of said space.
 8. A precipitator according toclaim 6 wherein said tubular elements widen upwardly.
 9. A precipitatoraccording to claim 5 wherein said cooling jacket means for maintainingthe outer element at a temperature lower than the inner element includesmeans for circulating a cooling liquid therethrough around said outerelement.
 10. A precipitator according to claim 3 wherein said tubes areflexible.
 11. A precipitator according to claim 10 wherein said tubularelements are vertical and said one end of the inner element is the lowerend thereof and the other end of the inner element is the upper endthereof, said precipitator further comprising a branch pipe forconveying fluid, said branch pipe being connected to the upper end ofthe inner element and to said tube at the upper end to interconnect thesame and means for raising and lowering the inner element within theouter element including means coupled to said branch pipe to raise andlower the same and the inner element therewith.